1. Technical Field of the Invention
The present invention relates to a gear-driven turbo compressor which increases a speed by a speed-up gear to rotationally drive a turbo compressor at a high speed.
2. Description of the Related Art
Turbo compressors may be largely classified into a “direct connection type” directly connecting an impeller of a turbo compressor to a rotation shaft of a motor and a “speed-up gear type” increasing a speed of a rotation of a motor, an engine, a turbine, or the like by a speed-up gear to rotationally drive an impeller of a turbo compressor at a high speed. Hereinafter, the speed-up gear type turbo compressor will be referred to as a “gear-driven turbo compressor”.
The gear-driven turbo compressor has the features that a multi-stage turbo compressor with three or more stages may be driven by a single drive source (a motor or the like), large capacity may be easily obtained compared to the direct connection type turbo compressor, reliability, compression efficiency, and mechanical efficiency are high, and maintenance is easy.
The direct connection type turbo compressor is disclosed in, for example, Patent Documents 1 to 5, and the gear-driven turbo compressor is disclosed in, for example, Patent Documents 6 and 7.
Furthermore, a “foil bearing” according to the invention is disclosed in, for example, Patent Documents 8 to 10 and Non-Patent Document 1, and a “dry seal” is disclosed in, for example, Patent Documents 11 and 12.
FIG. 1 is a partially cross-sectional view illustrating an existing gear-driven turbo compressor.
In this example, the gear-driven turbo compressor is a four-stage compressor, and is configured to obtain a high pressure gas by sequentially compressing an object gas by four impellers 16 (only two of them are shown in the drawing). Further, in this drawing, a compressor housing surrounding the impeller and a gas flow path are not shown.
In FIG. 1, the reference numeral 12 indicates a bull gear (a large gear), the reference numeral 14 indicates a pinion gear (a small gear), the bull gear 12 is rotationally driven by a driving device (a motor, an engine, a turbine, or the like) (not shown), and the speed of the pinion gear 14 is increased by the rotation, so that the impellers 16 attached to both ends thereof rotate at a high speed. The speed increasing ratio of the speed-up gear including the bull gear 12 and the pinion gear 14 is generally ten times or so, and each impeller rotates at high speed at about ten thousand rpm to several tens of thousands of rpm.
In FIG. 1, the reference numeral 18 indicates a thrust collar which is fixed to a pinion shaft 13 (a small gear shaft) with the pinion gear 14 interposed therebetween, and the reference numeral 20 indicates a thrust bearing which supports a thrust force of a large gear shaft 11. The thrust force acting on each impeller and the thrust force generated by the meshing portion between the bull gear and the pinion gear are transferred to the thrust bearing 20 via the thrust collar 18 and the bull gear 12 slidably supported therebetween.
Further, in this drawing, the reference numeral 15 indicates a gear box (a casing), the reference numeral 22 indicates a radial bearing, the reference numeral 23 indicates a gas seal, and the reference numeral 24 indicates an oil thrower (an oil seal).    [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-65286, “OIL-FREE COMPRESSOR”    [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-44954, “TURBO REFRIGERATING MACHINE HAVING COMPRESSOR WITH GAS BEARING AND ITS OPERATING METHOD”    [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-232289, “BEARING DEVICE AND ROTATION DRIVING DEVICE HAVING THE SAME”    [Patent Document 4] Japanese Patent Application Laid-Open No. 07-208456, “CENTRIFUGAL COMPRESSOR”    [Patent Document 5] Japanese Patent Application Laid-Open No. 08-232885, “BEARING GAS SUPPLY DEVICE”    [Patent Document 6] Japanese Patent Application Laid-Open No. 08-189494, “GEAR DRIVEN MULTI-SHAFT TURBO COMPRESSOR AND GEAR DRIVEN MULTI-SHAFT RADIAL EXPANDER”    [Patent Document 7] Japanese Patent Application Laid-Open No. 2008-231933, “GEAR DRIVEN TURBO COMPRESSOR”    [Patent Document 8] Japanese Patent Application Laid-Open No. 2001-295836, “FOIL TYPE FLUID BEARING”    [Patent Document 9] Japanese Patent Application Laid-Open No. 2004-263781, “FOIL BEARING AND METHOD OF USING THE SAME”    [Patent Document 10] Japanese Patent Application Laid-Open No. 2009-299748, “FOIL BEARING”    [Patent Document 11] Japanese Patent Application Laid-Open No. 2004-190783, “METHOD OF ACTIVATING DRY GAS SEAL TYPE ROTARY MACHINE AND DRY GAS SEAL TYPE ROTARY MACHINE”    [Patent Document 12] Japanese Patent Application Laid-Open No. 2007-177887, “CENTRIFUGAL COMPRESSOR AND DRY GAS SEAL SYSTEM USED THEREIN”    [Non-Patent Document 1] Robert J. Bruckner and Bernadette J. Puleo, “Compliant Foil Journal Bearing Performance at Alternate Pressures and Temperature”, NASA/TM, 2008-215219, GT2008-50174, May 2008